[DRAFT] V2 Kernel Invariants

[duncanita]

⚠ Draft RFC-backed issue.
Scope and architecture still under active review.
Do not implement without explicit validation.

Problem / Need

Define the execution invariants that make ruby-dag a reliable DAG execution kernel: deterministic runs, idempotent node execution, replayability, and clear boundaries between pure computation and effects.

Proposed scope

• Deterministic execution hashing
• Replayable scheduler
• Node idempotency contract
• Execution trace model

Acceptance criteria

• Same DAG definition + same input produce the same logical result hash.
• Re-running an idempotent node does not duplicate observable logical output.
• A run can be replayed and reconstruct the same state sequence.
• The kernel exposes calculation/effect boundaries without depending on LLM or host-specific code.

Draft sub-issues

• [DRAFT] Deterministic execution hashing
• [DRAFT] Replayable scheduler
• [DRAFT] Node idempotency contract
• [DRAFT] Execution trace model

Review notes

Move this issue from DRAFT/RFC to BACKLOG only after the architecture is accepted.